Page 60 - AERB

Table 1.12: INES Rating of Significant Events in NPPs For the purpose of analysis, the events reported
Reported during Calendar Year (2019) during year 2019 were also categorized as per the
IAEA-IRS coding system. The classification of systems
INES Rating of Events
NPPs failed / affected during the significant events is given in
INES-0 INES-1 Figure-1.8. The classifications of direct causes and root
TAPS-1 & 2 2 0 causes of the significant events are given in Figure-1.9
TAPS-3 & 4 3 0 & 1.10 respectively.
RAPS-1 & 2 7 1 • Significant Event Rated at Level-1 on INES is
RAPS-3 & 4 3 0 briefed below:
RAPS-5 & 6 6 0 On January 13, 2019, RAPS-2 was shut down
MAPS-1& 2 3 0 due to water leakage from secondary side of multiple
NAPS-1 & 2 1 0 boiler hairpins. The investigation was carried out after
KAPS-1 & 2 2 0 the shutdown revealed that leakage was due to generic
phenomenon (i.e. under deposit corrosion) which had
KGS-1 & 2 8 0
KGS- 3 & 4 1 0 led to wall thinning and pinholes in the boiler hairpins,
near the weld joint between tube-sheet and boiler
KKNPP-1&2 4 0 hairpin shell. After the event, the vulnerable area was
Total 40 1 inspected in all other boiler hairpins of RAPS-2 and
other similar units and requisite remedial measures were
* INES rating of one event at TAPS-3&4 is under review in
AERB. implemented.

I & C Systems
Primary Systems

Feedwater, 15%
Steam
and Power
Conversion
Systems

17% 44%

19%

Electrical Systems
5%

Essential Auxiliary
Systems

Fig. 1.8: Classification of Failed/Affected Systems of SERs

32 AERB Annual Report 2019